Zoogeography of the shallow‐water holothuroids of the western Indian Ocean

Abstract

Aim To analyse the zoogeography of the shallow-water holothuroids of the western Indian Ocean (WIO). Based on this analysis we ask to what extent differences in species' ability to disperse across potential barriers provide an explanation for holothuroid zoogeography.Location Shallow-waters (50 m isobaths) of the WIO, extending from Suez to Cape Town and from the coastline of East Africa upward to 65°E.Methods Data for the analysis were obtained from Samyn's (2003) monograph on the shallow-water sea cucumbers of the WIO. A species presence/absence matrix with a resolution of 1°latitude/longitude was constructed. These cells were assigned to eight coarser operational geographical units, which were delimited on the basis of published faunistic and geological borders. The analytical zoogeographical methods employed were cluster analysis on several b-diversity coefficients and parsimony analyses of endemicity. The influence of life-history strategies on the distribution pattern was analysed through examination of latitudinal and longitudinal gradients, and by plotting cumulative curves for species number against range size. ResultsThe shallow-water holothuroid fauna of the WIO can be split into several biogeographical units. To the north, we found evidence that the northern Red Sea holothuroid fauna differs from that of the southern Red Sea. The latter has closest affinity with south-east Arabia and the Persian Gulf, and thus the biogeographical barrier of Bab-el-Mandab nowadays seems to be of minor importance. The cold upwelling at the east coast of Somalia forms an effective barrier for holothuroids and especially those with lecitothrophic (short-lived) larvae. Even though the circumtropical biogeographical pattern is not well resolved, important taxonomic turnovers suggest that it is composed of several distinct subprovinces. Taxonomic turnover is at least partially dictated by the dispersion capacity of the different orders.Main conclusions This study concludes that the WIO is best split into at least three biogeographical realms: (1) the Red Sea and associated Arab Basin, (2) the asymmetrical circumtropical region stretching from the horn of Africa to southern Mozambique, and (3) southern Africa. Conspicuous differences in dispersal abilities of the three dominant orders are identified. The biogeography of the WIO is best explained by: (1) species' dispersion ability, (2) the prevalent current patterns, and (3) to a lesser, geographically limited extent, recent geological history. As a serendipitous discovery, we found that Rapoport's rule does not hold in the WIO.

Zoogeography of Intertidal Communities in the West Indian Ocean as Determined by Ocean Circulation Systems: Patterns from the Tetraclita Barnacles

“…Although previous studies in holothurians [16] not resolve the fine pattern within the circumtropical region, subdivisions are evident from taxonomic turnovers. These three putative biogeographic provinces are supported by our present analysis while fine subdivision is further revealed.…”

“…Based on the gene flow and distribution pattern obtained, we test the hypothesis whether the biogeography of intertidal barnacles is mainly affected by the major oceanographic patterns and less influenced by geological history in WIO [16].…”

Introduction to virtual issue on Red Sea and Western Indian Ocean biogeography

“…Rather, each taxon may have its own unique evolutionary history (even congeners may have different histories) with correspondingly unique mechanisms. We additionally include studies focused on an important transition zone along the South African coastline (Bustamante & Branch, 1996;Primo & Vazquez, 2004;Teske, Papadopoulos, Barker, McQuaid & Beheregaray, 2014), studies teasing apart key processes affecting both ancient (Fernandes, Rohling & Siddall, 2006) and more recent migration (Golani, 1993;Kiflawi, Belmaker, Brokovich, Einbinder & Holzman, 2006;Roberts, Shepherd & Ormond, 1992) within and out of the Red Sea, studies focused on the isolating effects of the Arabian Sea upwelling (Kemp, 1998;Schils & Coppejans, 2003), a study using holothuroids as a model to understand zoographical patterns in the Western Indian Ocean (Samyn & Tallon, 2005) and studies that remind us we must not now nor ever forget to consider the ecology of a system when defining biogeographical boundaries (Choat, 2006).…”

Patterns of Diversity, Areas of Endemism, and Multiple Glacial Refuges for Freshwater Crabs of the Genus Sinopotamon in China (Decapoda: Brachyura: Potamidae)

“…Many studies have suggested that multivariate methods can reveal informative biogeographical patterns [33], [34], [35], because one can reduce the inherent complexity of biogeographical data and obtain replicable results [36]. In this study, we analyzed diversity patterns of Sinopotamon using geographical information systems (GIS) and identified areas of endemism (AOEs) using a combination of parsimony analysis endemicity (PAE) and clustering analysis.…”